The present invention relates to halogen-containing resin compositions having excellent long-term thermal stability.
It is known that when halogen-containing resins, including polyvinyl halide and halogenated polyolefin, are subjected to light or to elevated temperature during or after compounding or processing, they can undergo a marked change in colour and transparency and become brittle owing to the occurrence of a decomposition reaction which is mainly attributable to the release of hydrogen halide.
Various stabilizers have been proposed for preventing such deterioration. Although zinc, lead, alkaline earth metal or organo tin stabilizers have been mainly employed, each of these stabilizers is not sufficient in long-term thermal stability. Among organo tetravalent tin stabilizers, particularly alkyl tin laurate and alkyl tin maleate stabilizers have been recognized as imparting excellent transparency to the end product made from halogen-containing resins. However, they are of high cost and are heavy metal stabilizers which are toxic, and hence it has become increasingly desirable to reduce the amount to be incorporated of in the halogen-containing resin from the standpoint of economical and social aspects.